(See \helpref{wxHtmlHelpController}{wxhtmlhelpcontroller} for help controller description.)
-A {\bf book} consists of three files : header file, contents file and index file.
+A {\bf book} consists of three files: header file, contents file and index file.
+You can make a regular zip archive of these files, plus the HTML and any image files,
+for wxHTML (or helpview) to read; and the .zip file can optionally be renamed to .htb.
\wxheading{Header file (.hhp)}